Various text editing systems and image processing systems are known, for example, European Patent Application 0 188 072 A1 and Gutknecht, "Concepts of the Text Editor LARA," Vol. 28, No. 9, Communications of the Association of Computing Machinery (September 1985). A text editor having a technique for defining line unit spacing is described in European Patent Application 0 199 908 A2 wherein a pop-down menu shows a command bar and menu of selectable parameters defining margins and spacing.
A system to prepare and manage documents to a model is available commercially in the form of a computer and a software package known as the "Workstation Publishing System" by Interleaf, Inc., Cambridge, Mass., U.S.A., and described, for example in "Is What You See Enough To Get?" by R.A. Morris (in: PROTEXT II: Proceedings of the Second International Conference on Text Processing System, Dublin, 1985, ISBN 0 906738 50X). In this system, the inputting means comprise a keyboard and a mouse. The mouse can be used by the operator to select a position on the screen, whereupon he can input commands or text at that place on the screen by using the keyboard. This system also uses menus which appear on the screen locally after a button on the mouse has been pressed and which comprise a set of commands from which the operator, again using the mouse, can select and execute one.
The known system enables the operator to prepare a document consisting of different components, such as headings, text blocks, footnotes etc. This document is displayed on the screen in a text window provided with a margin. A label with the name of that component is provided in that margin at the start of each component.
The external characteristics of each component, such as type face and size, margin positions, typographical functions, and so on, are fixed in the properties which may have a different setting or value for each component. The set of properties of a component may be displayed on the screen in a separate window by bringing it up via a menu with the mouse at the label of that component. This window also displays the values of the properties. These can be changed by the operator. If he does not change them, then the values pre-programmed by the supplier (default values) apply.
To increase legibility, the operator will often wish to make the appearance of certain components different, e.g., by printing the heading in bold and centered on the line. He can achieve this by giving the properties of that component a corresponding value.
This system has one basic component from which the operator can form a number of different components by giving one or more of the properties a different value. In that way he can define a number of components tailored to different applications in the document by means of properties which have different values from one another. By giving these components different names (the name of a component is also a property), he can make them distinguishable. A component specialized in this way can then be used at different places in a document.
At the operator's choice a change of the value of properties of a component can be made to apply to all the components with the same name as the amended component.
Components are built up of sub-components, e.g., letters. A sub-component also has properties which describe its appearance. As a rule these will have values (sub-local values) identical to those of the corresponding properties of the component to which the sub-component belongs (the local values), but sometimes they will differ, for example if a single word in a paragraph is printed in bold face or in italics.
A desktop publishing system of the type described above has the disadvantage that positioning of the graphic elements in the document to be prepared does not depend on special properties of the input document information, such as the presence of text elements to be positioned as subscripts and/or superscripts, specific mathematical symbols, a plurality of formats associated with letter fonts, and various formats associated with elementary constituents for creating drawings. The occurrence of specific document information results in a less attractive lay-out of the document to be prepared. The object of the present invention is to provide a solution to this problem.